Re: [Qemu-devel] [PATCH v2] net: Add support of VIRTIO_NET_F_GUEST_ANNOUNCE for vhost-net/vhost-user

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Jun 05, 2015 at 03:24:12PM +0200, Thibaut Collet wrote:
> Add VIRTIO_NET_F_GUEST_ANNOUNCE capability to vhost-net when netdev backend is
> vhost-user.
> 
> For netdev backend using virtio-net NIC the self announce is managed directly
> by the virtio-net NIC and not by the netdev backend itself.
> To avoid duplication of announces (once from the guest and once from QEMU) a
> bitfield is added in the NetClientState structure.
> If this bit is set self announce does not send message to the guest to request
> gratuitous ARP but let virtio-net NIC set the VIRTIO_NET_S_ANNOUNCE for
> gratuitous ARP.
> 
> Signed-off-by: Thibaut Collet <thibaut.collet@6wind.com>
> ---
> v2: do not discard anymore packets send to vhost-user: it is GARP request after
>     live migration.
>     As suggested by S. Hajnoczi qemu_announce_self skips virtio-net NIC that
>     already send GARP.
> 
>  hw/net/vhost_net.c |    2 ++
>  include/net/net.h  |    1 +
>  net/vhost-user.c   |    2 ++
>  savevm.c           |   11 ++++++++---
>  4 files changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index 426b23e..a745f97 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -82,6 +82,8 @@ static const int user_feature_bits[] = {
>      VIRTIO_NET_F_CTRL_MAC_ADDR,
>      VIRTIO_NET_F_CTRL_GUEST_OFFLOADS,
>  
> +    VIRTIO_NET_F_GUEST_ANNOUNCE,
> +
>      VIRTIO_NET_F_MQ,
>  
>      VHOST_INVALID_FEATURE_BIT
> diff --git a/include/net/net.h b/include/net/net.h
> index e66ca03..a78e9df 100644
> --- a/include/net/net.h
> +++ b/include/net/net.h
> @@ -85,6 +85,7 @@ struct NetClientState {
>      char *name;
>      char info_str[256];
>      unsigned receive_disabled : 1;
> +    unsigned self_announce_disabled : 1;
>      NetClientDestructor *destructor;
>      unsigned int queue_index;
>      unsigned rxfilter_notify_enabled:1;
> diff --git a/net/vhost-user.c b/net/vhost-user.c
> index 8d26728..b345446 100644
> --- a/net/vhost-user.c
> +++ b/net/vhost-user.c
> @@ -147,6 +147,8 @@ static int net_vhost_user_init(NetClientState *peer, const char *device,
>  
>          s = DO_UPCAST(VhostUserState, nc, nc);
>  
> +        /* Self announce is managed directly by virtio-net NIC */
> +        s->nc.self_announce_disabled = 1;
>          /* We don't provide a receive callback */
>          s->nc.receive_disabled = 1;
>          s->chr = chr;
> diff --git a/savevm.c b/savevm.c
> index 3b0e222..7a134b1 100644
> --- a/savevm.c
> +++ b/savevm.c
> @@ -80,11 +80,16 @@ static void qemu_announce_self_iter(NICState *nic, void *opaque)
>  {
>      uint8_t buf[60];
>      int len;
> +    NetClientState *nc;
>  
> -    trace_qemu_announce_self_iter(qemu_ether_ntoa(&nic->conf->macaddr));
> -    len = announce_self_create(buf, nic->conf->macaddr.a);
> +    nc = qemu_get_queue(nic);
>  
> -    qemu_send_packet_raw(qemu_get_queue(nic), buf, len);
> +    if (!nc->peer->self_announce_disabled) {
> +        trace_qemu_announce_self_iter(qemu_ether_ntoa(&nic->conf->macaddr));
> +        len = announce_self_create(buf, nic->conf->macaddr.a);
> +
> +        qemu_send_packet_raw(nc, buf, len);
> +    }
>  }
>  

I don't think qemu_send_packet_raw can ever work for vhost user.
What happens if you merely add VIRTIO_NET_F_GUEST_ANNOUNCE
to the feature list, and drop the rest of the patch?


> -- 
> 1.7.10.4